<PAGE>

                                                                Exhibit 10(dd)
 
                                   AGREEMENT

     AGREEMENT (this "Agreement"), dated as of August 7, 1998, by and between
Marc Tipermas, a resident of the State of Maryland ("Tipermas"), and ICF Kaiser
International, Inc., a Delaware corporation. As used in this Agreement, unless
the context indicates otherwise, the term "ICF" shall be deemed to refer to ICF
Kaiser International, Inc. and each and every one of its affiliated entities.

                                  WITNESSETH

     WHEREAS, Tipermas presently serves as a member of the Board of Directors
and President and Chief Operating Officer of ICF Kaiser International, Inc. and
as a director and officer of certain subsidiaries and affiliates of ICF Kaiser
International, Inc.; and

     WHEREAS, Tipermas and ICF Kaiser International, Inc. are parties to an
Employment Agreement dated May 19, 1997, including any attachments thereto and
any other agreements referred to therein or entered into pursuant thereto
(collectively, the "Executive Agreement"); and

     WHEREAS, Tipermas and ICF wish consensually to terminate the Exec Agreement
and sever the employment relationship between Tipermas and ICF.

     NOW, THEREFORE, in consideration of the premises and the mutual covenants
and promises hereinafter provided and of the actions taken pursuant thereto, the
parties agree as follows:
<PAGE>
 
     1.  Effective Date. This Agreement shall be executed and become effective
         ----------------                                                     
August 7, 1998 (the "Effective Date").

     2.  Termination of Executive Agreements. As of the Effective Date, the
         -----------------------------------                               
Executive Agreement shall be deemed terminated and shall have no further force
or effect. Tipermas and ICF agree that there are no existing defaults by either
party under the Executive Agreement and that, as of the Effective Date, each
party had fully performed all of its obligations to the other party under the
Executive Agreement.

     3.  Resignation and Termination of Existing Employment Relationship. As of
         ---------------------------------------------------------------       
the Effective Date, Tipermas shall be deemed to have resigned from all corporate
offices and the Board of Directors of ICF, and from all offices and
directorships of ICF's subsidiaries, joint ventures, and affiliated companies,
organizations, and entities. Subject only to the provisions of Section 6,
Tipermas's employment by ICF shall be deemed to have terminated as of the close
of business on the Effective Date.

     4.  Records and Bank Accounts. As soon as practicable after the Effective
         ---------------------------                                          
Date, ICF shall take such steps as may be necessary to (a) reflect in the
corporate records of ICF, its subsidiaries, joint ventures, and affiliated
companies, organizations, and entities that Tipermas has resigned as an officer
and director of ICF and as an officer and director of ICF's subsidiaries, joint
ventures, and affiliated companies, organizations, and entities; and (b) remove
Tipermas as an authorized signatory on all corporate bank accounts.

                                      -2-
<PAGE>
 
     5.  Payment for Cancellation of the Employment Agreement and Release. In
         ----------------------------------------------------------------    
consideration of the cancellation of the Executive Agreement and the execution
by Tipermas of the Release attached hereto, Tipermas shall be paid $732,500,
within seven business days of the Effective Date and by wire transfer or direct
deposit as directed by Tipermas, except that Tipermas hereby requests voluntary
withholding of Federal and state wage-type withholding in respect of such amount
(calculated as though such amount were wages and in accordance with Tipermas's
elections).

     6.  Consultation. During the period from the Effective Date until January
         -------------                                                        
31, 1999, Tipermas (or his estate in the event of his death) will receive
compensation at an annual rate of $375,000.00, which compensation shall be paid
to Tipermas in accordance with ICF's normal payroll practices, subject to
Federal and state wage-type deductions in accordance with Tipermas's elections.
During such period, Tipermas will consult with ICF on an as needed basis, such
consultations to be at times reasonably convenient to both Tipermas and ICF. ICF
shall reimburse Tipermas for reasonable expenses incurred with connection with
his consultation with ICF, subject to normal ICF reimbursement procedures.

     7.  Health and Insurance Benefits. Until January 31, 1999, Tipermas and his
         -----------------------------                                          
dependents shall receive the same health, welfare and life insurance benefits
that would have been made available to them had Tipermas continued as an
employee. Tipermas may elect to continue his family health benefits provided
through ICF to the extent permitted by Federal COBRA laws in effect on the
Effective Date. For purposes of COBRA compliance, the date on which Tipermas's
health benefits terminate shall be January 31, 1999.  Except as specifically

                                      -3-
<PAGE>
 
provided in this Section 7, all health, welfare and insurance benefits shall
terminate on January 31, 1999.

     8.  Options. ICF and Tipermas acknowledge and agree that (a) Tipermas holds
         --------                                                               
and shall continue to hold the following options to purchase shares of ICF
common stock granted pursuant to ICF's Stock Incentive Plan and (b) such options
have the expiration dates set forth below:
<TABLE>
<CAPTION>
                                                     Fully
               Total   Vested   Unvested  Vesting   Vested   Expiration
 Grant Date   Options  Options  Options   Schedule   Date       Date     Price
<S>           <C>      <C>      <C>       <C>       <C>      <C>         <C>
 
   4/4/94     114,940  114,940         0   4 years   4/4/98     11/1/99  $3.48
   4/4/94      10,060   10,060         0   4 years   4/4/98     11/1/99  $3.48
  1/24/97      26,400    6,600    19,800   4 years  1/24/01     1/24/02  $2.23
</TABLE>

Notwithstanding the terms of the grant of the options granted on January 24,
1997, such options shall be fully vested as of the Effective Date. All of the
options referred to in this Section 8 shall expire on November 1, 1999. Prior to
that date such options shall be exercisable by Tipermas or, in the event of his
death, his estate.

     9.  Restricted Stock. ICF and Tipermas acknowledge that Tipermas holds
         -----------------                                                 
9,900 shares of Restricted Stock granted to him pursuant to the ICF Stock
Incentive Plan on March 4, 1997, of which 3,300 shares are presently vested,
subject to a restriction on sale prior to March 4, 2000. The balance of 6,600
shares of such Restricted Stock shall be forfeited. Consistent with the terms of
the Executive Agreement, and pursuant to the ICF Stock Incentive Plan, Tipermas
is hereby awarded 150,000 shares of Common Stock which shall be issued, and
fully vested, on the 

                                      -4-
<PAGE>
 
first anniversary of the Effective Date or, if earlier, the occurrence of any
sale of the Company or all or substantially all of the Company's assets, or
other event resulting in a change of control of the Company which is reported on
a Form 8-K. Certificates for the shares of Restricted Stock referred to in the
immediately preceding sentence, shall be delivered to Tipermas (or, in the event
of his death, his estate) on the appropriate date referred to in the immediately
preceding sentence.

     10.  Indemnification and Notice Concerning Nonrenewal of Directors and
          -----------------------------------------------------------------
Officers Insurance Coverage.
----------------------------

     (a) ICF acknowledges that its Certificate of Incorporation and By-Laws and
the charters and by-laws of certain of its direct and indirect subsidiaries
include provisions designed to provide to former officers and directors
indemnification in respect of threatened and commenced actions, suits and
proceedings in which an individual is a party or is threatened to be made a
party by reason of the fact that he is or was an officer or director of ICF or
such subsidiaries. ICF shall, and shall cause such subsidiaries to, continue to
provide indemnification to Tipermas under such provisions to the maximum extent
permitted by applicable law.

     (b) So long as ICF maintains directors and liability insurance coverage,
Tipermas shall be covered by such insurance, with respect to his tenure with
ICF, on the same terms as other existing and former officers and directors. If,
for any reason, ICF shall not continue to have in effect directors and officers
liability insurance coverage, on terms substantially comparable to those
presently in effect, ICF shall provide Tipermas with written notice of the
cancellation or 

                                      -5-
<PAGE>
 
nonrenewal of such coverage not less than 20 days prior to the effectiveness of
such cancellation or nonrenewal.

     11.  Employment References. Nothing in this Agreement shall prevent either
          ----------------------                                               
party from stating the fact that Tipermas was employed by ICF, the address of
his work location, the dates of his employment, his job titles and job duties,
his rate of pay, or that he resigned from his position as an officer of ICF on
or about the Effective Date.

     12.  Proprietary Information and Business and Personal Property
          ----------------------------------------------------------

     (a) Tipermas will not directly or indirectly disclose any confidential
records, information, documents, data, formulae, specifications or other trade
secrets owned by ICF or its affiliates to any person, or use any such
information, except (a) as appropriate in connection with the consulting
activities contemplated by Section 6 or (b) pursuant to court order or as a
result of a valid order, subpoena or discovery request (and in the case of such
disclosure Tipermas will provide ICF with written notice of the same
sufficiently in advance of the required disclosure date to allow ICF to lodge
appropriate objections to such disclosure). The immediately preceding sentence
shall not apply to information: (a) disclosure of which is required by law or by
process lawfully issued; (ii) which has been disclosed to Tipermas or to a third
party by a person not under a duty of confidentiality with respect to that
information; or (iii) which later enters the public domain through no fault or
breach of duty by Tipermas.

     (b) Tipermas shall have no ownership interest in any records, files,
information, documents, or the like that belong to ICF or its affiliates which
Tipermas has used, prepared or 

                                      -6-
<PAGE>
 
come into contact with during his employment by ICF, and, except as appropriate
in connection with the consulting activities contemplated by Section 6, Tipermas
shall not remove written copies thereof from the premises of ICF or any of its
affiliates without ICF's written consent. Within five business days after the
Effective Date, Tipermas shall have returned to ICF all ICF property (other than
the cellular telephone and facsimile machine referred to in Section 12(c)) that
Tipermas has in his possession. Nothing in this Agreement shall limit Tipermas's
right to remove personal effects from his office within five business days after
the Effective Date.

     (c) Tipermas shall be entitled to the ICF-owned facsimile machine and
cellular telephone currently in Tipermas's possession, provided that, except as
                                                       ---------               
contemplated by Section 6, Tipermas shall be responsible for the cost of
cellular telephone service on such cellular telephone following the Effective
Date. Until December 31, 1998 or until Tipermas obtains new employment,
whichever occurs first, ICF will allow Tipermas to have access, from off ICF
premises, to his voice mailbox on the ICF telephone system and to Tipermas's ICF
e-mail address.

     13.  No Disparaging Statements. Each of ICF and Tipermas covenant and agree
          -------------------------                                             
that following the Effective Date neither shall make disparaging statements
concerning the other, or its officers, directors, affiliates, agents and/or
employees. For this purpose, a disparaging statement shall refer to a statement
or statements that, individually or in the aggregate, have a materially
detrimental effect on the business affairs of ICF or Tipermas, as the case may
be.

                                      -7-
<PAGE>
 
     14.  Confidentiality of Agreement.  Except as required by law or as
          ----------------------------                                  
necessary to fulfill the terms of this Agreement or the General Releases
incorporated herein, or in connection with a party's family, business, or tax
affairs (in which case disclosure shall be on a confidential basis to the extent
practicable), the parties shall not disclose the terms or provisions of this
Agreement or such General Releases, or the fact of their existence, to any
person or entity.

     15.  No Admissions. Nothing contained in this Agreement or the General
          -------------                                                    
Releases incorporated herein shall be considered an admission by either party of
any wrongdoing under any Federal, state or local statute, public policy, tort
law, contract law, common law or otherwise.

     16.  No Third Party Claims. Each party represents and warrants that no
          ----------------------                                           
other person or entity has, or to the best knowledge of such party claims, any
interest in any potential claims, demands, causes of action, obligations,
damages or suits released pursuant to this Agreement; that it or he is the owner
of all other claims, demands, causes of action, obligations, damages or suits so
released; that it or he has full and complete authority to execute this
Agreement; and that it or he has not sold, assigned, transferred, conveyed or
otherwise disposed of any claim, demand, cause of action, obligation or
liability subject to this Agreement and the General Releases contemplated
hereby.

     17.  Full Releases.  Each party agrees and acknowledges that the
          -------------                                              
consideration received by it or him for this Agreement and the General Releases
incorporated herein, and for the execution hereof and thereof, shall constitute
full payment, satisfaction, discharge,

                                      -8-
<PAGE>
 
compromise and release of and from all matters for which the other party has
mutually released it or him herein and in such General Releases.

     18.  Expenses.  ICF shall reimburse Tipermas for all fees and expenses of
          --------                                                            
Tipermas's counsel incident to the negotiation of this Agreement, up to a
maximum of $10,000. The amount of such reimbursement shall be considered a
payment and cancellation of rights under the Executive Agreement. Except as
provided in the first sentence of this Section 18, each party shall pay its own
costs incident to the negotiation, preparation, performance, execution, and
enforcement of this Agreement, and all fees and expenses of its or his counsel,
accountants, and other consultants, advisors and representatives for all
activities of such persons undertaken in connection with this Agreement.

     19.  No Third Party Beneficiaries.  Except as expressly stated herein, the
          -----------------------------                                        
parties do not intend to make any person or entity who is not a party to this
Agreement a beneficiary hereof, and this Agreement should not be construed as
being made for the benefit of any person or entity not expressly provided for
herein.

     20.  Advice of Counsel.  The parties acknowledge that they have been
          ------------------                                             
advised by competent legal counsel in connection with the execution of this
Agreement, that they have read each and every paragraph of this Agreement and
that they understand their respective rights and obligations.  Tipermas declares
that he has completely read this Agreement, fully understands its terms and
contents, and freely, voluntarily and without coercion enters into this
Agreement.

                                      -9-
<PAGE>
 
     21.  Entire Agreement.  This Agreement constitutes the entire agreement of
          -----------------                                                    
the parties with respect to the subject matter hereof, and all prior
negotiations and representations are merged herein or replaced hereby.

     22.  Severability.  If any provision of this Agreement is held illegal,
          -------------                                                     
invalid or unenforceable, such illegality, invalidity, or unenforceability shall
not affect any other provision hereof. Any such provision and the remainder of
this Agreement shall, in such circumstances, be deemed modified to the extent
necessary to render enforceable the remaining provisions hereof.

     23.  Governing Law.  This Agreement shall be construed and enforced in
          --------------                                                   
accordance with the law of the Commonwealth of Virginia.

     24.  Releases and Effectiveness.  This Agreement and General Releases in
          --------------------------                                         
the forms attached hereto as Exhibits A and B, which are incorporated' herein by
reference, have been executed by or on behalf of Tipermas and ICF on the dates
shown opposite their respective signatures below, and this Agreement and such
General Releases are effective as of the Effective Date.

     25.  Disputes.  In the event that any dispute arises between the parties
          --------                                                           
hereto pertaining to the subject matter of this Agreement and the parties are
unable to resolve such dispute within a reasonable time through negotiations,
the parties shall attempt to resolve such dispute pursuant to a mutually agreed
upon alternate dispute resolution mechanism.  Such resolution of the dispute
shall be initiated by written notice given by one party to the other.  If 

                                      -10-
<PAGE>
 
within 10 days after submission of such notice the parties have not agreed upon
an alternate dispute resolution mechanism, the dispute shall be submitted to
arbitration in Fairfax County, Virginia. In the event the parties are unable to
agree on an alternate dispute resolution mechanism and the dispute is to be
resolved pursuant to arbitration, each party shall appoint an arbitrator within
20 days after the original notice of the dispute, and the two arbitrators so
chosen shall promptly appoint a third arbitrator. If either party fails to name
an arbitrator as aforesaid, such arbitrator shall be designated by the American
Arbitration Association. If any arbitrator becomes disabled, resigns or is
otherwise unable to discharge the arbitrator's duties, the arbitrator's
successor shall be appointed in the same manner as such arbitrator was
appointed. The parties shall not be permitted to conduct discovery in connection
with the arbitration, and, subject only to the availability of the arbitrators,
the arbitration hearing shall be held within 30 days after appointment of the
third arbitrator. Except as aforesaid, the arbitration shall be conducted under
the applicable rules of the American Arbitration Association. Any determination
of the arbitrators shall be binding and conclusive upon the parties hereto.
Application may be made by either party to any court having jurisdiction thereof
for judicial confirmation of any determination by the arbitrators and/or for an
order of enforcement of any such decision.

     26.  Counterparts.  This Agreement may be executed in counterparts, all of
          ------------                                                         
which shall be considered one and the same agreement, and shall become effective
on the Effective Date.

                                      -11-
<PAGE>
 
     IN WITNESS WHEREOF, Marc Tipermas and ICF Kaiser International, Inc. have
executed this Agreement.

ICF KAISER INTERNATIONAL, INC.                  MARC TIPERMAS, Ph.D.
By:
   ------------------------------------         ---------------------------
     Its Duly Authorized Representative         Marc Tipermas, Ph.D.

Dated: August 7, 1998                           Dated: August 7, 1998

                                      -12-
<PAGE>
 
                                                                       EXHIBIT A

                                GENERAL RELEASE

     I, MARC TIPERMAS, on behalf of myself and my heirs, successors, agents,
executors, administrators, attorneys and assigns, in consideration of the terms
of the Agreement effective as of August 7, 1998 by and between ICF Kaiser
International, Inc. ("ICF") and myself (the "Agreement") and the execution of a
General Release ("Release") by ICF, with effect as of August 7, 1998, hereby
release and forever discharge ICF and any and all of its present, former and
future affiliated entities, subsidiaries, departments, officers, directors,
employees, representatives, agents, attorneys, successors and assigns, from any
and all claims and causes of action (whether known or unknown) which I have
against them, in law or equity, relating to or arising under: Federal, Virginia,
or other state or local law; any employment contract or related agreements; any
employment statute or regulation; any employment discrimination law, including
but not limited to Title VII of the Civil Rights Act of 1964, as amended, and
the Age Discrimination in Employment Act of 1967, as amended; the Employee
Retirement Income Security Act of 1974, as amended; any other Federal, state, or
local civil rights, pension or labor law; contract law; tort law; and common
law, including but not limited to wrongful discharge or misrepresentation or
infliction of emotional distress; provided however that I do not hereby release
                                  -----------------                            
ICF from any of its obligations under the Agreement and/or under the terms of an
employee benefit plan, program or arrangement (other than any such plan, program
or arrangement providing for the payment of severance benefits).  For purposes
of this Release, ICF shall be deemed to include each and every one of its
affiliated entities described in the Agreement.

                                      -13-
<PAGE>
 
     I further agree not to sue or otherwise institute or cause to be instituted
or in any way voluntarily participate in the prosecution of any complaints or
charges against any persons or entities released herein in any Federal, state,
or other court, administrative agency or other forum concerning any claims
released herein.

     Except as required by law or as necessary to fulfill the terms of the
Agreement or this Release, or as necessary in connection with personal business
or tax affairs (in which case disclosure shall be on a confidential basis to the
extent practicable), I agree not to disclose the terms or provisions of this
Release, or the fact of its existence, to any person or entity.

     I understand and agree that nothing contained in this Release is to be
considered an admission by ICF of any wrongdoing under any Federal, state, or
local statute, public policy, tort law, contract law, or common law.

     I acknowledge that I have been advised to consult with an attorney prior to
executing this Release. I further acknowledge that I have been given a period of
at least twenty-one (21) days within which to consider and execute this Release,
unless I voluntarily choose to execute this Release before the end of the said
twenty-one (21) day period. Once executed, I understand that I have seven (7)
days following the execution of this Release to revoke it, and that this Release
is not effective or enforceable until after said seven (7) day period.

                                      -14-
<PAGE>
 
     I acknowledge that I have read this Release, that I understand it, and that
I am executing it freely and voluntarily. I further understand that once this
Release becomes effective (after the seven (7) day revocation period), it can
only be altered, revoked or rescinded with the express written permission of
ICF.

     I further acknowledge and agree that, in the event I exercise my revocation
rights within the specified seven-day period, all rights and obligations under
this Release and the Agreement will become null and void.

     This Release is executed in connection with, and is subject to terms o
Agreement.

Date: August 7, 1998                    
                                        ----------------------
                                        Marc Tipermas


     Subscribed and sworn to before me this 7 day of August, 1998.


                                        ----------------------
                                        Notary


My commission expires: November 30, 2000
                       -----------------

                                      -15-
<PAGE>
 
                              ELECTION TO EXECUTE
                            PRIOR TO EXPIRATION OF
                      TWENTY-ONE DAY CONSIDERATION PERIOD

     I, Marc Tipermas, understand that I have at least twenty-one (21) days
within which to consider and execute the above General Release. However, after
consulting counsel, have freely and voluntarily elected to execute the General
Release before the twenty-one (21) day period has expired.                     I




Date: August 7, 1998           
                                        ----------------------
                                        Marc Tipermas

                                      -16-
<PAGE>
 
                                                                       EXHIBIT A

                                GENERAL RELEASE

     ICF Kaiser International, Inc. ("ICF"), on behalf of ICF and all of its
current, former or future affiliated entities, subsidiaries, departments,
officers, directors, employees, representatives, agents, attorneys, successors
and assigns, in consideration of the terms of the Agreement effective as of
August 7, 1998 by and between Marc Tipermas ("Tipermas") and ICF (the
"Agreement") and the execution of a General Release ("Release") by Tipermas,
with effect as of August 7, 1998, hereby releases and forever discharges
Tipermas and his heirs, successors, agents, executors, administrators, attorneys
and assigns, from any and all claims and causes of action (whether known or
unknown) which ICF has against him, in law or equity, relating to or arising
under: Federal, Virginia or other state or local law; any employment contract,
any employment statute or regulation, contract law, tort law; and common law,
including but not limited to actions for fraud and breach of contract; provided,
                                                                       -------- 
however, that ICF does not hereby release Tipermas from any of his obligations
-------                                                                       
under the Agreement.

          ICF will not sue or otherwise institute or cause to be instituted or
in any way voluntarily participate in the prosecution of any complaints or
charges against Tipermas or the other person released herein in any Federal,
state, or other court, administrative agency or other forum concerning any
claims released herein.

          Except as required by law or as necessary to fulfill the terms of the
Agreement or this Release, or as necessary in connection with ICF's business or
tax affairs (in which case 

                                      -17-
<PAGE>
 
disclosure shall be on a confidential basis to the extent practicable), ICF
agrees not to disclose the terms or provisions of this Release, or the fact of
its existence, to any person or entity (including employees of the Company).

     ICF understands and agrees that nothing contained in this Release is to be
considered an admission by Tipermas of any wrongdoing under any Federal, state,
or local statute, public policy, tort law, contract law, or common law.

     ICF acknowledges that this Release can only be altered, revoked or
rescinded with the express written permission of Tipermas.

     This Release is executed in connection with, and is subject to the terms
of, the Agreement.


                                    ICF KAISER INTERNATIONAL, INC.


Date: August 7, 1998                By:
                                       --------------------------------
                                    Its Duly Authorized Representative


Subscribed and sworn to before me this 7th day of August, 1998.
 

                                       --------------------------------
                                       Notary


My commission expires:  November 30, 2000

                                      -18-